A liquid crystal display (LCD) device has various advantages, for example, a high resolution, low driving voltage, low power consumption, thin thickness, small volume and light weight as compared with a cathode ray tube (CRT) device, making it ideal for use in a variety of applications, such as portable computers, communication devices, mobile devices, television sets, etc.
Generally, the LCD device includes two main parts: a liquid crystal panel and a backlight module. The backlight module is employed for providing planar light source of a uniform luminance into the LCD panel. When such a light is incident into the panel from the backlight module, a uniform image is displayed through an entire effective display area of the panel.
The backlight assembly may include a light guide plate and a light source for generating light. For example, the light source may be a cold cathode fluorescent lamp (CCFL) or a light emitting diode (LED). The LED is usually employed for a display device having a relatively small display unit, such as a mobile communication device, to thereby reduce the volume and the power consumption thereof. It is observed that large-size LCD TVs on the market are starting to adopt LEDs as backlight.
FIG. 1 is a side view of a conventional LED backlight module 100, which includes a LED light source 102 and a light guide plate 104. A light generated from the LED typically corresponds to a point light and has a large divergent angle θ, around 110 to 120 degrees (measured based on FWHM of the luminosity). However, the thickness of the light guide plate 104 is around 0.4 to 2.0 mm, which is quite thin relative to the large divergent angle of the LED light source 104, so that only a limited portion of light is coupled into the light guide plate 104, resulting in low coupling efficiency.
The conventional solutions increase the brightness or the numbers of LED to increase the total output from backlight module. However, inevitably they would add up the manufacture cost and make the circuit design more complicated. Therefore, it is desired to have a new, inexpensive, and simple-implemented backlight module to solve aforementioned problems.